The present invention relates to a high resistance flexible floating boom.
This boom is in particular suitable for defining shipping zones or water areas, either on the water surface, or throughout the whole water depth (for moderate water depths which may reach 20 meters, for example).
Such water areas may be for example, used as swimming areas, or for other aquatic activities, or also for "aquaculture".
A very important application of the invention is for fighting against water pollution caused by floating solid wastes or by water soluble or immiscible chemical products, more particularly hydrocarbons.
Most of the booms presently used are constituted by horizontal floats supporting a watertight skirt provided with ballast weights for holding such skirts down.
A main disadvantage of this type of boom is that they cannot practically prevent the passage of hydrocarbons spread on the water surface as a result of their limited height above the water level. Moreover, their watertight skirt cannot prevent passage of the hydrocarbons under the boom caused by a vortex effect when the speed of the water current exceeds 1 or 2 knots.
Another type of prior art floating boom is also known which comprises a structure supported by floats on both sides of the water level in an upright position and adapted to constitute a barrier.
However, such booms have points of reduced resistance and are likely to be rapidly destroyed in rough sea conditions.
It is known to use in such a boom structure, longitudinal cables adapted, in particular, to withstand traction loads as described in French Pat. No. 2,101,606, in the Publication "Offshore", volume 32 of June 5, 1972, pages 69 and 70, as well as in the German Published Patent Application OS No. 2,051,711.
However, in such prior art structures the traction loads are not uniformly distributed over the whole height of the boom structure and, as a result, the boom structure may consequently be subjected to deformations due to differences in the respective traction loads at the different levels of the boom. More particularly, such loads can be caused by the water currents, from swell and winds, etc. The boom could be turned upside down as a result of the action of these different stresses.
It is also known in a boom to associate traction resistant elements with floats, as described in U.S. Pat. No. 3,921,407 and French Pat. No. 2,226,852, but in such booms the floats are not isolated from the traction loads to which the boom structure is subjected, and this requires either building floats of very high mechanical resistance which are thus heavier, of higher cost and of reduced buoyancy, or alternatively, risking the rupture of a float, which would cause severe damages to the boom.
It is also known from U.S. Pat. No. 3,882,682 to secure the floats to rigid vertical support members to isolate these floats from traction loads, but the structure described in this patent does not provide for a substantially uniform distribution of these traction loads over a plurality of longitudinal elements specially adapted to withstand such traction loads. Therefore, the differences in the traction loads supported by the boom at different levels thereof may cause the boom to turn upside down.
The boom described in U.S. Pat. No. 3,924,412 comprises a skirt which is subjected directly to the traction loads applied to the boom. This requires selecting, for the construction of the boom, a highly resistant material which must be of sufficient thickness to withstand these traction loads.
This structure, is consequently heavier and more expensive than a structure having spaced traction resisting elements. Moreover the increased weight makes it more difficult to maintain the boom in a balanced operative position when it is subjected to the different loads generated by the wind, currents and swell.